I was referring to the design using Delta IV size tanks with Atlas kerosene engines. Goes back a long way.

Vulcan is just the latest iteration of the idea...

Later! OL J R

I disagree that Vulcan is simply "the latest iteration." The concept you're talking about was conceived as an ultra-heavy lift vehicle a la Ares (at least the triple-core version was...). It was a vehicle in search of a market (and that market is only the US Government). Vulcan is driven by two imperatives - first, to move away from RD-180. It's amazing, after years of constant abuse from Senator McCain regarding that engine, that we now have Senator Paul saying we need to keep buying them. The safest bet, regardless of which side of the argument you prefer, is to ditch RD-180. The second imperative is, of course, reducing costs. Government launches ebb and flow - so that means doing more commercial launches to remain solvent. Atlas V gets a bad rap. Nobody reports the launch costs correctly (always high, based on "bad math"). Nevertheless, Vulcan is designed from the outset with low cost in mind.